Development of high repetition rate VUV lasers
Abstract
The work described in this thesis was aimed at developing a field of
expertise in short wavelength lasers within the department of Physics and
Astronomy at St. Andrews University. Electrical discharge pumping was
selected as the excitation mechanism while the Lyman band of hydrogen
was identified as the initial target for the vacuum ultraviolet work. Due
to the short upper state lifetime of the laser transition (~0.8ns), fast
voltage pulse risetimes and an accurately timed, travelling electrical
excitation wave matched to the speed of light in the discharge were
required.
Initial work succeeded in producing voltage pulses at high
repetition rates having leading edges exhibiting risetimes of under
300psec with voltage magnitudes in the 30-40kV regime. This was
achieved by designing and building non-linear ferromagnetic shock lines
whose purpose was to sharpen the output pulse from a thyratron having a
risetime of 40-50ns. Voltage pulse risetime reductions on this magnitude
have not been seen previously in the literature by this author. By the
accurate timing of the outputs of ten such lines placed in parallel, the
travelling electrical excitation wave could be created. Allied to work
conducted simultaneously upon flat plate Blumlein driven hydrogen
lasers, this culminated in the production and operation of a thyratron
driven, sectional longitudinal hydrogen laser capable of high repetition
rates. This is the first of its type of which this author is aware.
Laser pulse energies of 4.7μJ on the 160nm Lyman band transitions
were observed while the only limitation encountered in running the laser
at multi-kilohertz repetition rates in burst mode was that imposed by the
charging rate of the available power supply. Despite this, 1kHz operation
of a hydrogen laser was amply demonstrated for the first time.
Type
Thesis, PhD Doctor of Philosophy
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